precision lr rifle

Hi all I want to put to gether accurate long range rifle so far I hawe used a
custom 300 win mag and I also hawe a 338 edge the 300 wm has been more accurate so far for this project I ordered a bat L2R action with two bolts
one for 30 378 weatherby one for cheytac i will use mcmillan 50 LBR stock
1,75 x 32 inch krieger 30 cal barrel and lothar walther 1,6 x32 for 338 cal
I will use norma brass for 30 378 what brass is good for a 338 cheytac based
cartridge ?